Such a valve device may consist of a valve body and a plunger for directing the controlling and/or controlled fluid to and from the device. Typically, O-ring seal means is provided, between the body parts and between the bore wall and plunger, which seal means is passed by the plunger or passes over a port to effect the desired valving action. Peters et al U.S. Pat. No. 3,044,492 discloses a pilot valve embodying such an arrangement in which O-rings on the valve plunger move in and out of an enlarged valve chamber to selectively connect a pressured fuel inlet to one or the other outlet leading to a controlled device. If the O-ring seal, when in the valve chamber, is exposed to extremely high pressure, say 10,000 p.s.i., there is a danger that the seal ring will be extruded from its groove to render the device inoperative under certain conditions.